Ok, like everyone else, I have watched the What the Health documentary on Netflix, as well as a bunch of other Vegan propaganda documentaries lately, and have plant based eating on my mind.
And while I am not a full on vegan, I do eat a largely plant based diet and respect the ethical and environmental reasons underlying the vegan lifestyle. With the popularity of vegan films on the rise, I thought this was an ideal time to update this BCO1 post. Vegans, like their paleo brethren, love to insist that their diet is the healthiest for all people, which is the antithesis of the Gene Food message. Our goal is to highlight bio-individuality.
It depends on the person. Let me illustrate this point by discussing the very different ways people metabolize beta carotene.
BCO1: the beta carotene gene
One of the fascinating things about genetic research is the opportunity it affords to study the metabolic efficiencies of the human body.
Many of our “nutritional inputs” have to change form before they’re useful as fuel for our cells, and our genes play an important role in helping to produce the enzymes that break down nutrients into a form the body can use. For example, it’s the VDR genes that help to make the active form of vitamin D, called calcitrol, so it can be used to absorb calcium from the gut. Similarly, our MTHFR genes help us break down folate into 5-MTHF (methyl folate).
This article discusses our BCO1 genes, and how they influence the body’s ability to convert beta-carotene into an active form of Vitamin A, called retinol.
Vitamin A: plant and animal sources
Vitamin A is a powerful antioxidant responsible for supporting healthy skin, vision, bone growth, and immune function, among other things. We can get Vitamin A from both plant and animal sources. (R) Eggs, for example, are rich in a form of Vitamin A called retinol. Retinol, famous in many circles as the main ingredient in anti-aging skin treatments, is readily bioavailable, meaning it is consumed in a form the body can make use of right away.
The other source of Vitamin A comes from fat soluble antioxidants known as carotenoids, which are plant based. Beta carotene, found in foods like carrots and yams, is a type of carotenoid that our bodies convert to Vitamin A (retinol). (R)
See also: Bioavailability of lycopene
We are easily able to absorb retinol derived from animal products, however, the bioavailability of plant based sources is more limited, meaning we lose Vitamin A in the process of converting beta-carotene to retinol. (R)
This is where the possibility for a vitamin A deficiency comes into play, especially for vegans. Since our bodies aren’t as effective at breaking down plants into vitamin A, a diet that excludes all animal based products could set the table for a Vitamin A deficiency.
This possibility increases when certain variants in our BCO1 genes are present.
BCO1 Genes and Vitamin A
There is genetic variability in B-carotene metabolism. Some process beta-carotene into Vitamin A more efficiently than others. (R) The protein encoded by the BCO1 gene, called beta-carotene 15,15′-monoxygenase (BCMO1), is a key enzyme in beta-carotene metabolism to vitamin A. (R)
Two common SNPs of the BCO1 gene, (R267S and A379V) have shown a decreased ability to metabolize beta carotene into retinol. (R) Just as certain SOD2 A16V alleles result in lower amounts of superoxide dismutase, certain BCO1 variations result in lower amounts of BCMO1, and therefore reduced amounts of bioavailable Vitamin A for carriers.
The “risk” allele for BCO1 R267S is T.
The “risk” allele for BCO1 A379V is also T.
Note: to date, the studies showing a decreased ability to convert beta-carotene to Vitamin A for these SNPs have only been performed in women, the evidence is inconclusive as to men. (R)
For those with genotypes associated with a reduced ability to gain vitamin A from plant sources, a vegan diet could present some nutritional challenges, because some studies show that vitamin A supplementation isn’t a great solution either.
The flip side: retinol from animals and supplements not necessarily healthy for women
We’ve established there are genetic variants of the BCO1 gene that put women at a disadvantage in accessing Vitamin A from plants.
Does this mean Vitamin A supplements, or even animal sources of Vitamin A are advisable?
For starters, studies show diets (we’re talking food here) high in carotenoids are healthy, and may reduce the risk of certain diseases.
This study discusses the protective effect dietary beta-carotene can have on developing many types of cancers.
This study analyzed dietary beta-carotene’s protective impact on heart disease.
This study discusses how dietary Vitamin A can protect against macular degeneration.
This study saw an increased risk for lung cancer and heart disease of 20% when beta carotene consumption exceeded the recommended dosage.
This study found a significant increase in hip fracture risk in postmenopausal women taking Vitamin A supplements and retinol in fortified food. To quote the study:
Long-term intake of a diet high in retinol may promote the development of osteoporotic hip fractures in women. The amounts of retinol in fortified foods and vitamin supplements may need to be reassessed.
It’s also important to note that dietary beta-carotene, as opposed to Vitamin A supplements, did not increase the risk for fracture.
As we’ve discussed, our BCO1 genotype plays a role in how easy it is for our bodies to get Vitamin A from beta-carotene. Most of the science surrounding beta-carotene’s health benefits studied sources of beta-carotene derived from food, as opposed to supplements. Vitamin A from animal sources, in the form of retinol, is readily absorbed by the body, but these sources are not available to vegans.
Vitamin A is an important nutrient, and deficiency can be a health issue, although it is rare. (R) Food is the best source of Vitamin A, although smaller doses of Vitamin A may be beneficial for some people. (R)
Dr. Ben Lynch’s Strata Gene product recommends considering Vitamin A supplementation for BCO1 A379V (+/+, TT) females, especially if vegan:
TT Females showed a reduced ability to convert beta carotene by 32%. Note: The intrinsic variability in the BCO1 activity is found in men as well, presumably due to the same SNPs, but currently there is no published research that examines a male population to investigate the impact. Consider Vitamin A supplementation especially in vegan individuals.
Consider combining dietary beta-carotene with healthy fats
Hesitant to take vitamin A supplements?
Short of eating an egg, or occasional piece of fish, or chicken, dietary fat could to be the answer to increasing Vitamin A levels for vegans.
Beta-carotene is a carotenoid, which is a fat soluble nutrient. Studies have shown large increases in bioavailability of beta-carotene when it’s taken with fat. Foods like avocado, or olive oil, can be an excellent companion to high beta carotene foods like yam and carrots.
Now, I know what you’re saying: if I have a BCO1 SNP, aren’t I unable to convert beta carotene to Vitamin A? If so, what good does more beta carotene do?
Yes, some BCO1 SNPs at a disadvantage in actually metabolizing beta-carotene, and it’s not clear if more bioavailable beta-carotene is the answer, it’s my theory, however, as with any nutrigenomic “mutation,” BCO1 is associated with reduced function, not zero function, you’ll still be converting some of the beta carotene to the Vitamin A your body can use.
If you’re a vegan unsure of how best to optimize your Vitamin A levels for optimal health, see a doctor (who knows something about nutrition).